A vehicle-mounted noise reduction method, system and storage medium for narrowband noise
Through the improved vehicle noise reduction method based on momentum term, the vehicle audio system is used to quickly offset the engine noise in the car, solving the problems of poor noise reduction effect and slow convergence speed in the existing technology, and achieving efficient noise control.
Patent Information
- Application Number
- CN202210062885.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-01-19
- Publication Date
- 2024-12-24
- Estimated Expiration
- 2042-01-19
AI Technical Summary
The prior art has poor noise reduction effect on low-frequency noise in vehicle noise control, especially engine noise in the car, and the convergence speed of active noise reduction algorithms such as LMS and momentum-based FxLMS is slow, making it difficult to quickly reduce noise pollution.
Using an improved vehicle noise reduction method based on momentum term, by generating two reference signals and control signals, secondary sound waves are formed using the vehicle audio system, and the filter coefficients are updated to quickly offset the noise in the target area and improve the convergence speed.
On the basis of ensuring noise reduction, the convergence speed of the algorithm is significantly improved, noise pollution is reduced, and the listening comfort of drivers and passengers is improved, without adding additional computing resources or car counterweight.
Smart Images
Figure CN114530140B_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of vehicle-mounted noise control and relates to a vehicle-mounted noise reduction method and system and a storage medium for narrow-band noise. Background Art
[0002] With the development of modern industry, noise pollution has attracted more and more attention, and high-intensity noise signals have also affected the comfort of listeners. Due to the effect of sound masking, the volume needs to be increased to obtain a higher signal-to-noise ratio and a clear listening effect. The long-term high sound pressure caused by this will cause irreversible damage to hearing. With the improvement of vehicle intelligence, drivers and passengers have increasingly stringent requirements for the acoustic environment in the car. The noise in the car will reduce the comfort of the driver and passengers, causing irritability and fatigue of the passengers in the car; it will also affect the clarity of communication calls, and even affect the driver's perception of the signal sound outside the car, increasing traffic hazards. Automobile NVH (Noise, Vibration, Harshness) is an important issue that car manufacturers are concerned about. Reducing noise by modifying the structural design, adding damping materials or using devices such as shock-absorbing springs is collectively referred to as passive noise control; this method has a better noise reduction effect on mid- and high-frequency noise. However, this method has a poor effect on low frequencies, especially the noise of the engine in the car, which is often concentrated in low frequencies. In addition, passive noise control requires a long time to adjust and it is difficult to control costs. The active noise reduction solution uses the vehicle's audio system to create a counter-signal to the noise signal, forming a secondary sound wave to offset the noise in the target area, reduce noise pollution, and improve subjective listening comfort. However, it adds almost no extra weight to the vehicle, helps reduce exhaust emissions, and is a green, energy-saving solution.
[0003] The LMS algorithm is a traditional vehicle-mounted active noise reduction solution, but its convergence speed is slow. Subsequently, a momentum-based FxLMS (Filtered-x, Least Mean Square) algorithm was proposed, which adds a momentum term due to the increase in weight coefficients to the traditional LMS algorithm. Although the momentum-based FxLMS algorithm improves the convergence speed of the traditional LMS algorithm, the convergence speed of this method is still slow. Summary of the invention
[0004] The object of the present invention is to provide a vehicle-mounted noise reduction method and a vehicle-mounted noise reduction system for narrowband noise, which can actively reduce the noise of the vehicle engine, reduce the noise pollution in the vehicle and have a faster convergence speed.
[0005] The present invention also provides a computer-readable storage medium storing a program capable of implementing the above-mentioned vehicle-mounted noise reduction method.
[0006] According to a first aspect of the present invention, a vehicle-mounted noise reduction method for narrowband noise comprises the following steps:
[0007] A. Generate two reference signals x1(n) and x2(n) according to the angular frequency ω0 of the target noise to be reduced, where n represents the time;
[0008] B. Generate a control signal y(n) according to the following formula (1) and feed it to the sound reproduction device.
[0009]
[0010] Among them, w i (n) represents the filter coefficient at the current moment;
[0011] C. Filter the reference signal obtained in step A to obtain the filtered reference signal shown in the following formula (2):
[0012]
[0013] Where k = 0, 1, ... N-1, N represents the length of the filter, s k represents the coefficient of the transfer function model filter of the secondary channel; the transfer function of the secondary channel is a mathematical model of the transmission path from the sound playback device to the sound signal acquisition device, x i (nk) represents the value of the first k sampling moments of the i-th reference signal;
[0014] D. Update the filter coefficients according to the following formula (3-1) or (3-2):
[0015]
[0016]
[0017] Among them, μ represents the convergence factor, e(n) represents the error signal in the sense of signal processing, λ represents the constraint factor, and w i (n-1) represents the filter coefficient at the previous sampling time, w i (n+1) represents the filter coefficient at the next sampling time.
[0018] In a preferred embodiment, in step A, the two reference signals x1(n) and x2(n) are respectively expressed as follows:
[0019] x1(n)=sin(ω0n)
[0020] x2(n)=cos(ω0n).
[0021] In a preferred embodiment, in step B, the sound playback device is a vehicle-mounted speaker.
[0022] In a preferred embodiment, in step D, the error signal e(n) is collected by a vehicle-mounted microphone.
[0023] In a preferred embodiment, the target noise to be reduced is the noise caused by the vehicle engine.
[0024] According to a second aspect of the present invention, a vehicle-mounted noise reduction system for narrowband noise includes a sound playback device and a sound signal collection device, and the vehicle-mounted noise reduction system also includes:
[0025] A reference signal generation module, which is used to generate two reference signals x1(n) and x2(n) according to the angular frequency ω0 of the target noise to be reduced, where n represents the time;
[0026] A control signal generating module, which is used to receive the reference signal output by the reference signal generating module, and generate a control signal y(n) according to the following formula (1), and feed it to the sound playback device,
[0027]
[0028] Among them, w i (n) represents the filter coefficient at the current moment;
[0029] A filter module is used to filter the reference signal output by the reference signal generation module to obtain a filtered reference signal as shown in the following formula (2):
[0030]
[0031] Where k = 0, 1, ... N-1, N represents the length of the filter, s k represents the coefficient of the transfer function model filter of the secondary channel; the transfer function of the secondary channel is a mathematical model of the transmission path from the sound playback device to the sound signal acquisition device, x i (nk) represents the value of the first k sampling moments of the i-th reference signal; and
[0032] A filter coefficient updating module is used to receive the acoustic signal collected by the acoustic signal collecting device as an error signal, receive the filtered reference signal output by the filter module, and update the filter coefficient according to the following formula (3-1) or (3-2), and feed it to the filter module.
[0033]
[0034]
[0035] Among them, μ represents the convergence factor, e(n) represents the error signal in the sense of signal processing, λ represents the constraint factor, and w i (n-1) represents the filter coefficient at the previous sampling time, w i (n+1) represents the filter coefficient at the next sampling time.
[0036] In a preferred embodiment, the sound reproduction device comprises a vehicle-mounted speaker, and the vehicle-mounted speaker is arranged in a vehicle compartment.
[0037] In a preferred embodiment, the acoustic signal collecting device comprises a vehicle-mounted microphone, and the microphone is arranged in a vehicle compartment.
[0038] In a preferred embodiment, the target noise to be reduced is the noise caused by the vehicle engine.
[0039] According to a third aspect of the present invention, a computer-readable storage medium stores a computer program, which, when executed by a processor, implements the vehicle-mounted noise reduction method as described above.
[0040] Herein, the target noise to be reduced is the narrowband noise caused by the vehicle engine. The above-mentioned vehicle speakers are placed in the vehicle compartment or at least radiate sound to the vehicle compartment, including but not limited to: headrest speakers, ceiling speakers, door panel speakers, etc.; the above-mentioned microphones are placed in the vehicle compartment or at least can collect sound signals in the vehicle compartment.
[0041] The microphone is placed in the vehicle compartment or at least can collect sound signals in the vehicle compartment.
[0042] The present invention adopts the above solution, which has the following advantages compared with the prior art:
[0043] The vehicle-mounted noise reduction method and vehicle-mounted noise reduction system for vehicle engine narrowband noise of the present invention improve the momentum-based FxLMS algorithm, while ensuring a noise reduction amount equivalent to that of the traditional FxLMS algorithm and the momentum-based FxLMS algorithm, improves the convergence speed of the algorithm and does not occupy more computing resources; in addition, the vehicle-mounted audio system is used to construct an anti-signal of the noise signal to form a secondary sound wave, which offsets the noise in the target area, reduces noise pollution, and improves subjective listening comfort. BRIEF DESCRIPTION OF THE DRAWINGS
[0044] In order to more clearly illustrate the technical solution of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.
[0045] Figure 1 Flow chart of a vehicle-mounted noise reduction method according to Embodiment 1 of the present invention.
[0046] Figure 2 FIG. 4 is an algorithm block diagram of a vehicle-mounted noise reduction method according to Embodiment 1 of the present invention.
[0047] Figure 3 Schematic diagram of a vehicle-mounted noise reduction system according to Embodiment 1 of the present invention.
[0048] Figure 4 Flow chart of a vehicle-mounted noise reduction method according to Embodiment 2 of the present invention.
[0049] Figure 5 FIG. 4 is an algorithm block diagram of a vehicle-mounted noise reduction method according to Embodiment 2 of the present invention.
[0050] Figure 6 It is a noise reduction simulation comparison chart of the traditional FxLMS algorithm, the momentum-based FxLMS algorithm, Example 1 and Example 2. DETAILED DESCRIPTION
[0051] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention.
[0052] Different from passive noise control, the traditional LMS algorithm can use the vehicle audio system to construct the anti-signal of the noise signal, form a secondary sound wave, offset the noise in the target area, reduce noise pollution, and improve subjective listening comfort, but it hardly adds extra weight to the car, which helps to reduce exhaust emissions and is a green and energy-saving solution. However, the traditional LMS algorithm converges slowly and requires more than 4,000 iterations to achieve the target noise reduction. Based on this, the momentum-based FxLMS algorithm is proposed. A momentum term is added to the traditional LMS algorithm due to the increase in weight coefficients, and the expression of the momentum term is given:
[0053] w(n+1)=w(n)-2u w f(n)x(n)+α[w(n)-w(n-1)]
[0054] As early as 2014, Harbin Institute of Technology proposed a momentum-based LMS algorithm for narrowband noise control, Afiltered-x weighted accumulated LMS algorithm: Stochastic analysis and simulations for narrowband active noise control system. Its expression is
[0055]
[0056]
[0057] The last term in the above expression is the momentum term. However, the convergence speed of this momentum-based FxLMS algorithm is still slow.
[0058] Example 1
[0059] This embodiment provides an improved vehicle-mounted noise reduction method based on momentum term, which targets narrow-band noise caused by vehicle engines and further improves the convergence speed of the algorithm, making it converge faster than the traditional FxLMS algorithm and the momentum-based FxLMS algorithm, while achieving a noise reduction effect equivalent to that of the traditional algorithm, with little increase in calculation amount and without occupying too much calculation data. Figure 1 A flow chart showing the method is shown, Figure 2 FIG. 4 is a block diagram of the improved momentum-based FxLMS algorithm of this embodiment. Figure 1 and Figure 2 The vehicle-mounted noise reduction method is specifically described as follows.
[0060] (1) Reference signal generation: At each sampling moment, a reference signal, namely a sine signal and a cosine signal, is generated according to the angular frequency ω0 of the target noise to be reduced. The target noise to be reduced is the noise caused by the vehicle engine in the vehicle compartment.
[0061] This embodiment uses a function method to generate a reference signal:
[0062] x1(n)=sin(ω0n)
[0063] x2(n)=cos(ω0n)
[0064] (2) Control signal generation: Based on the current parameter w i(n) and the reference signal obtained in the previous step are used to generate a control signal y(n), which is fed to the sound reproduction unit such as the speaker of the vehicle audio system. The speaker is a vehicle-mounted speaker placed in the vehicle cabin, which is used to play secondary sound waves into the cabin in the hope of offsetting the noise caused by the engine in the cabin.
[0065]
[0066] (3) Generate a filtered reference signal: An important step in the FxLMS algorithm is to filter the reference signal. It is generally believed that the transfer function of the secondary channel includes the transmission path of the digital control signal y(n) through the DAC module, analog filter, power amplifier module, speaker, spatial propagation of sound waves, microphone, analog filter, and ADC module. The transfer function S of the secondary channel is obtained through online and offline system identification methods, expressed as S′, which is a digital filter with a length of N, expressed as S′=[s1, s2, …s N ] The filtered reference signal is calculated as
[0067]
[0068] (4) For parameter w i (n) Update: The momentum term is mainly modified. The specific expression is:
[0069]
[0070] like Figure 3 As shown, the vehicle-mounted noise reduction system according to this embodiment includes a sound playback device 101, a sound signal acquisition device 102, a reference signal generation module 103, a control signal generation module 104, a filter module 106 and a filter coefficient update module 107. The sound playback device 101 is specifically a vehicle-mounted speaker of the vehicle-mounted audio system, which is arranged in the vehicle compartment 100. The vehicle-mounted speakers include but are not limited to: headrest speakers, ceiling speakers, door panel speakers, etc. The sound signal acquisition device 102 includes a microphone for collecting error signals, which is arranged in the area of the vehicle compartment 100 where noise reduction is required. The reference signal generation module 103 is used to generate two reference signals x1(n) and x2(n) according to the angular frequency ω0 of the target noise to be reduced, where n represents the time.
[0071] The control signal generating module 104 is used to receive the reference signal output by the reference signal generating module 103, and generate a control signal y(n) according to the following formula. The control signal is converted into an analog signal by a digital-to-analog converter and fed to the sound reproduction device 101 via the power amplifier 105 to form a secondary sound wave for offsetting the engine noise in the vehicle compartment.
[0072]
[0073] Among them, w i (n) represents the filter coefficient at the current moment.
[0074] The filter module 106 is used to filter the reference signal output by the reference signal generation module 103 to obtain a filtered reference signal as shown in the following formula: The filter module 106 specifically includes a control filter, and the “filter coefficients” mentioned herein specifically refer to the coefficients of the control filter.
[0075]
[0076] Where k = 0, 1, ... N-1, N represents the length of the filter, s k represents the coefficient of the transfer function model filter of the secondary channel; the transfer function of the secondary channel is a mathematical model of the transfer path from the sound playback device 101 to the sound signal collection device 102, x i (nk) represents the value of the first k sampling moments of the i-th reference signal.
[0077] The filter coefficient updating module 107 is used to receive the acoustic signal collected by the acoustic signal collecting device 102 as an error signal, receive the filtered reference signal output by the filter module 106, and update the filter coefficient according to the following formula, and feed it to the filter module 106:
[0078]
[0079] Among them, μ represents the convergence factor, e(n) represents the error signal in the sense of signal processing, λ represents the constraint factor, and w i (n-1) represents the filter coefficient at the previous sampling time, w i (n+1) represents the filter coefficient at the next sampling time.
[0080] Example 2
[0081] Considering the amount of calculation, the algorithm in Example 1 is further improved, mainly in the parameter update part, without considering the coupling effect between the reference signals after filtering, it is assumed that i≠j, that is, the two signals are orthogonal. At this time, the parameter update of the algorithm is expressed as
[0082]
[0083] Combination Figure 4 and Figure 5 The vehicle-mounted noise reduction method of this embodiment is specifically described as follows.
[0084] (1) Reference signal generation: At each sampling moment, a reference signal, namely a sine signal and a cosine signal, is generated according to the angular frequency ω0 of the target noise to be reduced.
[0085] This embodiment uses a function method to generate a reference signal:
[0086] x1(n)=sin(ω0n)
[0087] x2(n)=cos(ω0n)
[0088] (2) Control signal generation: Based on the current parameter w i (n) and the reference signal obtained in the previous step to generate a control signal y(n), which is fed to the sound reproduction unit in the car
[0089]
[0090] (3) Generate a filtered reference signal: The transfer function of the secondary channel includes the transfer path of the digital control signal y(n) through the DAC module, analog filter, power amplifier module, speaker, spatial propagation of sound waves, microphone, analog filter, and ADC module. The transfer function S of the secondary channel is obtained through online and offline system identification methods and is expressed as S'. It is a digital filter with a length of N, expressed as S' = [s0, s1, ...s N-1 ] The filtered reference signal is calculated as
[0091]
[0092] (4) For parameter w i (n) Update: The momentum term is mainly modified. The specific expression is:
[0093]
[0094] The vehicle noise reduction system of this embodiment is basically the same as that of Embodiment 1, except that the filter coefficient updating module 107 updates the filter coefficient according to the following formula.
[0095]
[0096] Simulation Example
[0097] The convergence performance of the algorithm is simulated. In the simulation experiment, the target noise (such as Figure 6The original noise shown in FIG. 1 is a single-frequency signal with a frequency of 120 Hz, which is a frequency within the typical control frequency band encountered in active noise control, especially in vehicle-mounted active noise control. Considering the actual noise environment, the environmental noise is set to white noise. The signal-to-noise ratio of the entire noise signal is 10 dB. The simulation of active noise control is carried out using the traditional FxLMS algorithm, the momentum-based FxLMS algorithm, and the improved MFxLMS algorithm of Example 1 and Example 2. Figure 6 The relationship between the residual noise energy and the number of iterations of the adaptive control algorithm is given. Figure 6 It can be seen that the traditional FxLMS algorithm can effectively reduce noise, but the algorithm converges relatively slowly, and it takes 10,000 iterations to achieve 8dB of noise reduction; the momentum-based FxLMS algorithm converges faster, and converges after 6,000 iterations, and can achieve a noise reduction equivalent to that of the traditional FxLMS algorithm; and the improved momentum-based FxLMS algorithm proposed in Example 1 converges faster, and converges after 2,500 iterations, and can achieve a noise reduction equivalent to that of the traditional FxLMS algorithm; further, the simplified improved momentum-based FxLMS algorithm of Example 2 can also converge within 2,500 iterations, but the noise reduction performance is slightly worse during the convergence process.
[0098] Those skilled in the art will appreciate that, unless otherwise stated, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present application refers to the presence of features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.
[0099] The above embodiment is only for illustrating the technical concept and features of the present invention, and is a preferred embodiment. Its purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit of the present invention should be included in the protection scope of the present invention.
Claims
1. A vehicle-mounted noise reduction method for narrowband noise, comprising the following steps: A. Generate two reference signals x1(n) and x2(n) according to the angular frequency ω0 of the target noise to be reduced, where: n represents the time; B. Generate a control signal y(n) according to the following formula (1) and feed it to the sound reproduction device. Among them, w i (n) represents the filter coefficient at the current moment; C. Filter the reference signal obtained in step A to obtain the filtered reference signal shown in the following formula (2): Where k = 0, 1, ... N-1, N represents the length of the filter, s k represents the coefficient of the transfer function model filter of the secondary channel; the transfer function of the secondary channel is a mathematical model of the transmission path from the sound playback device to the sound signal acquisition device, x i (nk) represents the value of the first k sampling moments of the i-th reference signal; Characterized in that the vehicle-mounted noise reduction method further comprises the following steps: D. Update the filter coefficients according to the following formula (3-1) or (3-2): Among them, μ represents the convergence factor, e(n) represents the error signal in the sense of signal processing, λ represents the constraint factor, and w i (n-1) represents the filter coefficient at the previous sampling time, w i (n+1) represents the filter coefficient at the next sampling time.
2. The vehicle-mounted noise reduction method according to claim 1, characterized in that: In step A, the two reference signals x1(n) and x2(n) are respectively expressed as follows: x1(n)=sin(ω0n) x2(n)=cos(ω0n).
3. The vehicle-mounted noise reduction method according to claim 1, characterized in that: In step B, the sound playback device is a vehicle-mounted speaker.
4. The vehicle-mounted noise reduction method according to claim 1, characterized in that: In step D, the error signal e(n) is collected by a vehicle-mounted microphone.
5. The vehicle-mounted noise reduction method according to claim 1, characterized in that: The target noise to be reduced is the noise caused by the vehicle engine.
6. A vehicle-mounted noise reduction system for narrowband noise, comprising a sound playback device and a sound signal collection device, characterized in that: The vehicle-mounted noise reduction system also includes: A reference signal generation module, which is used to generate two reference signals x1(n) and x2(n) according to the angular frequency ω0 of the target noise to be reduced, where n represents the time; A control signal generating module, which is used to receive the reference signal output by the reference signal generating module, and generate a control signal y(n) according to the following formula (1), and feed it to the sound playback device, Among them, w i (n) represents the filter coefficient at the current moment; A filter module is used to filter the reference signal output by the reference signal generation module to obtain a filtered reference signal as shown in the following formula (2): Where k = 0, 1, ... N-1, N represents the length of the filter, s k represents the coefficient of the transfer function model filter of the secondary channel; the transfer function of the secondary channel is a mathematical model of the transmission path from the sound playback device to the sound signal acquisition device, x i (nk) represents the value of the first k sampling moments of the i-th reference signal; and A filter coefficient updating module is used to receive the acoustic signal collected by the acoustic signal collecting device as an error signal, receive the filtered reference signal output by the filter module, and update the filter coefficient according to the following formula (3-1) or (3-2), and feed it to the filter module. Among them, μ represents the convergence factor, e(n) represents the error signal in the sense of signal processing, λ represents the constraint factor, and w i (n-1) represents the filter coefficient at the previous sampling time, w i (n+1) represents the filter coefficient at the next sampling time.
7. The vehicle-mounted noise reduction system according to claim 6, characterized in that: The sound reproduction device includes a vehicle-mounted speaker, and the vehicle-mounted speaker is arranged in a vehicle compartment.
8. The vehicle-mounted noise reduction system according to claim 6, characterized in that: The acoustic signal collecting device comprises a vehicle-mounted microphone, and the microphone is arranged in a vehicle compartment.
9. The vehicle-mounted noise reduction system according to claim 6, characterized in that: The target noise to be reduced is the noise caused by the vehicle engine.
10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, which, when executed by a processor, implements the vehicle-mounted noise reduction method according to any one of claims 1 to 5.